Efforts are proceeding in the field of regenerative medicine for regenerating cells, tissues or organs and recovering their functions that were lost due to illness or accident and the like by using artificially cultured cells and tissues. In particular, a search is being made for safe and effective cells that are compatible with transplantation for use in treatment of lifestyle diseases such as arteriosclerosis, myocardial infarction, liver cirrhosis or diabetes as well as refractory diseases for which there are no effective therapeutic drugs such as Parkinson's disease or muscular dystrophy.
Mesenchymal stem cells (MSC) are cells that have the ability to differentiate into different types of various mesenchymal cells such as adipocytes, osteocytes, chondrocytes, fibroblasts or myoblasts, and since they permit autologous transplantation, are one of the cells that are expected to be applied to regenerative medicine.
Although mesenchymal cells are known to exist in human bone marrow as mesenchymal stem cells derived from bone marrow, since the number of such cells that can be separated and purified from bone marrow is extremely low, methods are attracting attention that enable mesenchymal stem cells to be obtained in large quantities from other body tissues, and particularly adipose tissue (referred to as adipose-derived stem cells (ADSCs)). ADSCs separated from adipose tissue have been reported to have the ability to multidifferentiate into adipocytes and osteocytes as well as immunotolerance (Non-Patent Documents 1 to 4).    Non-Patent Document 1: Zuk, P. A. et al., Mol. Biol. Cell, 13: 4279-4295, 2002    Non-Patent Document 2: Zuk, P. A. et al., Tissue Eng., 7: 211-228, 2001    Non-Patent Document 3: Rodriguez, A. M. et al., J. Exp. Med., 201: 1397-1405, 2005    Non-Patent Document 4: Qu-Petersen, et al., J. Cell. Biol., 157: 851-864, 2002
However, various types of cells such as neurocytes, vascular cells and adipocytes are also present in addition to ADSCs in human adipose tissue, and it is difficult to efficiently separate ADSCs from this tissue.
In addition, although ADSCs separated from adipose tissue have the ability to multidifferentiate, it is known to be extremely difficult to induce differentiation of ADSCs into myoblasts as compared with inducing their differentiation into adipocytes or osteocytes. Myoblasts fuse together to form tubular myotubes, and as they continue to differentiate, they ultimately become precursor cells that form skeletal muscle, and are useful cells in regenerative medicine.
Thus, an object of the present invention is to separate and collect mesenchymal stem cells that differentiate into myoblasts as efficiently as possible and in large quantities as an alternative to ADSCs.